Polyester textile fabrics and yarns are normally dyed in a multistep procedure using organic pigments dispersed in water with an anionic surfactant. In step 1, the fabric or yarn is immersed in a hot (e.g. 135.degree.C) dye bath comprising from about 0.1 to 12 weight percent of the organic pigment dispersed in water made acidic (pH 4.5 or less) with a water-soluble organic acid, such as acetic or oxalic acid. In step 2 , the dye bath is drained and the dyed fabric scrubbed with hot aqueous caustic and sodium hydrosulfite or preferably with hot (e.g. 80.degree.C) water having from 2-5 weight percent of a chlorinated solvent dispersed therein (e.g. perchloroethylene). In step 3, the aqueous waste stream from step 2 is discharged and the fabric is rinsed with hot (e.g. 80.degree.C) water. In step 4, the rinse water is discharged and the fabric partially dried by vacuum or by centrifical force. The dyed fabric is then usually dried in a forced-air oven and stored for further processing.
In each of steps 1- 4 above, an aqueous waste stream is generated that contains residual amounts of the dispersed organic dye. Ecological considerations obviously prohibit direct discharge of these waste streams. However, no satisfactory economical method has been heretofore available to purify (decolorize) waste streams containing dispersed organic dyes.